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relo999

Possible Sega CD model 1 power problem

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I've recently acquired a asian model 1 sega CD which at first sight the only problem with it was the fuse, but now I've replaced the fuse but it still doesn't power on. Occupationally it flickers its lights for a second (about once every 50 times) but nothing more.

 

I do use a regular (euro) megadrive 1 AC adapter for it but for the megadrive it self I use a AC adapter for the model 2 master system (which seems to work fine on just the megadrive).

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I've did some extra checking as I expected maybe the fuse blew again by repeated attempts at rebooting, which was just just fine.

 

But the thing I did notice was odd as there was no voltage at the fuse (at least to me seemed odd I'm not a electric engineer or might be using the voltage meter incorrectly)

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before and after the fuse, both before (and both after) the fuse and some random point's in the system.

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I've taken a look inside again, this time with more knowing what I did. The adapter does give power to the board, or at the very least partially, as the voltage regulator does work (14 in / 13 out).

Apart from that I've dissembled the whole system (except for the CD area) to for something out of the ordinary, nothing much except for some slight roughness of the power board on the underside under the heat-sink and the battery being replace and soldered with wire into place (but that seems to just fine from the looks of it).

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before and after the fuse isnt going to do much except measure the voltage drop across the fuse, millavolts you need to put black to a ground point (like the heat sink of the power board since you have it open

 

while you are in there see what the voltage regulator is putting out (the 3 pins on the part of the heatsink, middle is ground)

Edited by Osgeld

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the voltage regulator in and out all say ~13,5V and the fuse ~14V. How can I check if the other boards get any voltage?

Edited by relo999

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It looks like this, how can I remove that and replace that? And could I just replace it with a regular 5V 7805 voltage regulator?

 

7805voltage_Regulator_Sega_Cd.png

Edited by relo999

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I just noticed my own stupidity. I've checked the whole power board and I aperently checked the wrong thing.

power_board.png

The actual voltage regulator says ~0.1V in / 0.01V~ out. Which it obviously shouldn't, on both sides, so there seems to be something else wrong...

Edited by relo999

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I think I might have found the problem. The diode give voltage before it the arrow-ish part ~0.2V and after the input voltage ~14V.

 

So should there be a voltage difference between both sides of the diode (D1)?

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diode will only conduct one way, and you should be getting 14V minus, eh best guess 0.7v (depends on type of diode and current draw)

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I'm asking as I don't seem to get any voltage after the left side of the DC jack, or after TR3.

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From what I've read, you can bridge TR4 and it will work...it will just turn on regardless of whether the power switch is on or not. It would at least allow you to further test the unit.

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